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According to research done by Washington State University (WSU), EC motors were developed to deal with such problems as not having access to three-phase ac power, phase-shifting, and friction and wear problems that might come with electromechanical commutators.
As the study noted, “Three-phase ac power is not available everywhere and the frequency and voltage are constant, which makes speed control difficult. Single-phase power has all the shortcomings of three-phase power.
“In addition, phase-shifting methods produce an imperfect rotating field and tend to introduce losses in the motor. Many of the phase-shifting methods produce a weak starting torque.”
According to the study, an electromechanical commutator solves several of these problems.
“It can accomplish wide-range speed control, and it can provide high starting torque. The limitation is that the electromechanical commutator has friction and wear that (can) reduce efficiency and re-quire frequent maintenance. Also, some sort of voltage controller has to be used to accomplish speed control.”
All those factors lead WSU researchers to state, “Electronic commutation potentially eliminates all the above problems. Power is pulsed on and off electronically with semiconductor devices, sometimes called electronic switches, transistors, or by various acronyms that denote their design particulars.
“The pulsed signals power three or more circuits or coil groups within the motor. By varying the timing and duration of the pulses, the electronic controller can accomplish speed control and maintain high torque at start or over a broad speed range.”
INDUSTRY OFFERINGSSome industry manufacturers have been announcing their versions of EC motors, as well as expanding applications.
One of the most recent such announcements came from Heatcraft Refrigeration Products, which said EC replacement motors are now available for Bohn, Larkin, Climate Control, and Chandler brand units through its InterLink™ commercial refrigeration parts brand.
EC motors help lower energy costs and improve unit cooler performance, the company said. “The motors are up to 85 percent efficient, with test data showing a 51-60 percent increase over shaded pole motors and a 30-40 percent increase over permanent split capacitor (PSC) motors.”
As an aftermarket product, EC motors can be used as a drop-in replacement for existing shaded pole and PSC motors, the company said.
“Our customers are constantly challenged with finding new technologies to help make their current products more energy efficient,” said Ray Clarke, director of InterLink parts.
“We’re committed to helping with comprehensive aftermarket offerings that provide significant advantages to meet customer needs in the areas of energy savings, while continuing our long-standing commitment to green initiatives.”
CALIFORNIA FACTORIn introducing the motor to four brand-name unit coolers, Heatcraft said the coolers are now California Energy Commission Title 20 compliant.
The development is significant. Title 20 comprises energy conservation legislation that mandates improved efficiency in many industrial and commercial products and applications, including energy design standards. Other states and the federal government’s National Energy Policy have said they have already or will be adopting the California standards.
Thus, compliance with California standards is, in effect, compliance with national standards.
For more information, visit www.heatcraftrpd.com or www.interlinkparts.com.
Publication Date: 10/01/2007